Our overall objective is to improve the costly long-term course of mechanical low back pain (LBP). In recent work we found that people in both classification-specific and non-specific treatment groups displayed clinically meaningful improvements in pain and function, but differences between groups were smaller than expected. A possible reason for the attenuated group differences can be found in 3 related facts: 1) in addition to specific or non-specific exercise, both groups received training aimed at modifying the pattern of movement and alignment used in the lumbar spine during functional activities, 2) adherence levels were higher and more prolonged for training in functional activities than for exercise, and 3) outcomes continued to improve for about 6 months after the treatment phase but then gradually reversed along with declines in adherence to training in functional activities. In the current project we will capitalize on the effect of training people to modify their movement and alignment patterns during daily functional activities. This will be done by using a motor skill training program which emphasizes challenging practice in performance of functional activities painlessly with appropriate patterns of movement and alignment. We will also attempt to prolong the beneficial effects of the motor skill training by including a booster treatment 6 months after the initial treatment. To accomplish this we will conduct a prospective, randomized, controlled clinical trial in which people with chronic LBP will be randomized to a treatment of either motor skill training or commonly prescribed, evidence-based, strength and flexibility exercises. Treatment will be provided in 2 phases: 1) initial phase: 6 - 1 hour sessions, once/week for 6 weeks, and 2) booster phase: 1-3 sessions beginning 6 months after the initial phase. We will collect 1) pain, functional limitation, disability, and economic outcomes, 2) reports of adherence, and 3) instrumented measurements of movement and alignment patterns during functional activities. People will be followed for 12 months after the initial treatment phase. We will test 1 if motor skill training results in better outcomes and better adherence than strength and flexibility exercise in the 12 months after treatment, and 2) the effect of a booster treatment provided 6 months after the treatment phase on functional limitations and adherence to treatment. Finally we will examine the relationship between functional limitations and 1) treatment adherence, and 2) movement and alignment patterns displayed during functional activities. Expected outcomes from this project are specific recommendations for the use and timing of motor skill training during functional activities for people with LBP. Successful completion of this project will have an immediate, high impact on rehabilitation research and treatment of people with LBP. In addition, the approach described could be used to study other similarly long-term, costly, and function-limiting musculoskeletal pain conditions.